In general, if the internal temperature of an internal combustion engine, particularly a cylinder wall temperature or a combustion chamber temperature becomes low at a time of starting the internal combustion engine, a friction loss with respect to a motion of a piston is increased, and the composition of exhaust gas is deteriorated.
Accordingly, a warming-up device has been conventionally proposed that is structured such that a latent heat storage material is accommodated in the interior of an internal combustion engine, heat generated by the operation of the internal combustion engine is stored in the heat storage material, and the heat stored in the heat storage material is radiated at the next start of the internal combustion engine so as to promote the warming-up of the internal combustion engine (for example, refer to Patent Document 1).
The warming-up device is provided with a nucleation device having a pair of electrodes inserted to the interior of the heat storage material, and prompts a phase change in the heat storage material under a supercooled state so as to radiate heat from the heat storage material, by applying an electric voltage to the electrodes from the outside so as to operate the nucleation device.
However, in the conventional structure, since the phase change is prompted in the heat storage material by applying an electric voltage to the electrodes, it is necessary to provide a through port for inserting the electrodes to the interior of the heat storage material from the outside, and an electric circuit for applying the electric voltage to the electrodes, and the like. Accordingly, a machining operation for forming the through port passing through the interior of the heat storage material and the outside is necessary, and a seal around the through port is also necessary. Further, since the electric circuit is necessary, the costs inevitably increase.
Patent Document 1: Japanese Laid-Open Patent Publication No. 11-182393